The present invention relates to a novel phenylenediamine derivative which is suitably used as an electric charge transferring material, particularly hole transferring material in applications such as solar battery, electroluminescent device, electrophotosensitive material and the like, and an electrophotosensitive material using the same which is used for image forming apparatuses such as electrophotographic copying apparatus, laser beam printer and the like.
As the electric charge transferring material used for the above applications, there have been known carbazole compound, oxadiazole compound, pyrazoline compound, hydrazone compound, stilbene compound, phenylenediamine compound, benzidine compound and the like.
These electric charge transferring materials are normally used in a state at which they are dispersed in a membrane of a suitable binding resin.
In case of an electrophotosensitive material, there are widely used so-called organic photosensitive materials (OPC) such as:
a single layer type photosensitive material comprising a single layer photosensitive layer wherein the above electric charge transferring material and an electric charge generating material which generates an electric charge due to light irradiation are dispersed in a binding resin;
a multi-layer type photosensitive material comprising an electric charge transferring layer which contains an electric charge transferring material and an electric charge generating layer containing an electric charge generating material, and the like.
Such an organic photosensitive material has an advantage that it can be easily produced than an inorganic photosensitive material using an inorganic semi-conductor material, and has a wide selection of its material such as electric charge generating material, electric charge transferring material, binding resin, etc., thereby allowing a large latitude in functional design.
As the phenylenediamine compound being electric charge transferring material, an m-phenylenediamine derivative of the following formula (2) or a p-phenylenediamine derivative of the following formula (3) is generally used. ##STR2## wherein R.sup.5, R.sup.6, R.sup.7 and R.sup.8 are the same or different and are selected from the group consisting of: hydrogen atoms, alkyl groups, alkoxy groups, halogen atoms and aryl groups which may have a substituent or not.
In the p-phenylenediamine derivative of the general formula (3), two nitrogen atoms, which form the central skeleton of molecule as well as the central benzene ring, are substituted by the benzene ring at the p-position. This causes a higher symmetric property of the molecular structure, thus being poor in compatibility with binding resin. In addition, its electric charge transferring capability is insufficient.
On the other hand, in the m-phenylenediamine derivative of the general formula (2), two nitrogen atoms which form the central skeleton of molecule as well as the central benzene ring, are substituted by the benzene ring at the m-position. Thus its symmetric property is lower than the p-phenylenediamine derivative.
However, as to the m-phenylenediamine derivative wherein each of the substituents R.sup.5 to R.sup.8 in the formula (2) is substituted with the 4-positions of phenyl groups, there has not succeeded yet in decreasing the symmetric property of the molecular structure to a desirable level, resulting in an insufficient compatibility with binding resin.
Accordingly, although the material itself is estimated to be excellent in electronic charge transferring capability, an electrophotosensitive material using this as an electric charge transferring material can not fully exhibit that excellent electric charge transferring capability, thus being insufficient in photosensitivity.
In contrast, the m-phenylenediamine derivative wherein the substituents R.sup.5 to R.sup.8 are substituted with the 3-positions of phenyl groups exhibits a lower symmetric property of the molecular structure, thus being excellent in compatibility with binding resin. However, its electric charge transferring capability is insufficient.
Therefore, an electrophotosensitive material using this as an electric charge transferring material fails to show a sufficient photosensitivity.